patch 8.2.3545: setcellwidths() may make 'listchars' or 'fillchars' invalid

Problem:    setcellwidths() may make 'listchars' or 'fillchars' invalid.
Solution:   Check the value and give an error. (closes #9024)
diff --git a/src/optionstr.c b/src/optionstr.c
index 7f2b04d..3afb3db 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -871,7 +871,7 @@
 	if (check_opt_strings(p_ambw, p_ambw_values, FALSE) != OK)
 	    errmsg = e_invarg;
 	else if (set_chars_option(curwin, &p_fcs) != NULL)
-	    errmsg = _("E835: Conflicts with value of 'fillchars'");
+	    errmsg = _(e_conflicts_with_value_of_fillchars);
 	else
 	{
 	    tabpage_T	*tp;
@@ -881,7 +881,7 @@
 	    {
 		if (set_chars_option(wp, &wp->w_p_lcs) != NULL)
 		{
-		    errmsg = _("E834: Conflicts with value of 'listchars'");
+		    errmsg = _(e_conflicts_with_value_of_listchars);
 		    goto ambw_end;
 		}
 	    }